A rotary stapling machine of the aforesaid kind is known to the art and is constructed to apply staples to a material at predetermined distances apart along a material web with the aid of a stapling cylinder, a counterpressure cylinder, a forming drum, a horn which extends around the peripheral surface of the stapling cylinder between the forming drum and the counterpressure cylinder, and a stapling fork which, in coaction with the stapling cylinder, functions to cut staple forming wire-like material in the region between the stapling cylinder and the forming drum and to form a U-shaped staple, which is carried by the stapling fork and the stapling cylinder to the region between the stapling cylinder and the counterpressure cylinder and there fastened to a continuous web of material passing between the stapling cylinder and the counterpressure cylinder, with the aid of a die or anvil mounted on the counterpressure cylinder. A rotary stapling machine of the aforesaid kind is used to staple together multi-page newspapers, magazines or the like along the spine-parts thereof, and forms one processing station, among several, for processing printed matter exiting from a printing machine.
The printed paper material is folded in different ways to produce a newspaper, magazine or the like, and the individual pages and sheets are joined together by means of spine-related staples.
Rotary stapling machines of the aforesaid kind have earlier comprised a die which is fixedly mounted to the counterpressure cylinder and which includes two mutually adjacent grooves having a form which guides the legs of the U-shaped staple along curved grooves in the die as the legs are curved, wherein the free ends of the legs are curved back towards the intermediate part of the staple which joins said lets together, so as to clamp the legs against the material or paper sheets, preferably between the ends of the legs and the centre region of said leg connecting part.
A rotary stapling machine of the aforedescribed construction is known from a machine retailed by Tolerans Ingol Sweden AB, Tyreso, Sweden, under the designation "Tolerans" or "Ingol" adapted for newspapers.
In the following, a staple which when compressed exhibits the curved shape that a fixed die of the aforesaid kind imparts to the staple will be referred to as a "roller staple".
However, other devices adapted for other applications and which, in many respects, provide better securement of the material with staples where the staple legs are brought to a flattened state as the staple is compressed and are orientated in a more or less parallel relationship with the leg-joining part by being bent within a limited region also belong to the known prior art.
This type of staple will be referred to in the following as a "flat staple".